1. Field of the Invention
The present invention relates generally to method and system for testing VoIP devices. More particularly, the present invention relates to method and system for measuring density of VoIP devices.
2. Background Art
Subscribers use speech quality as the benchmark for assessing the overall quality of a telephone network. VoIP (Voice over Internet Protocol or Packet Network) devices, which are placed at the edge of the packet network, perform the task of encoding (speech compression) and decoding (speech decompression) for communication of speech data over the packet network. Each VoIP device includes a certain number of channels, where each channel includes an encoder for encoding speech signals for transmission over the packet network, and a decoder for receiving the encoded speech data over the packet network and generating decoded speech data. A VoIP device has a processing power, which is typically defined by millions of instructions per second (MIPS) that the VoIP device can execute. The density of a VoIP device is defined based on the number of channels that the VoIP device can process given the total MIPS. In the conventional approach, the density of a VoIP device is determined by measuring the MIPS consumed for processing one channel, and then the total MIPS of the VoIP device is divided by the MIPS consumed for processing the one channel to determine the VoIP density. For example, if a VoIP device has a processing power of 1,000,000 MIPS, and processing one channel consumes 10,000 MIPS, the density of the VoIP is determined to be 1,000,000/10,000 or 100. In other words, it is assumed that the VoIP device would be capable of handling 100 channels simultaneously. Therefore, if the VoIP includes 120 channels, the VoIP device would be unable to process some channels when the voice traffic exceeds the processing power of the VoIP device.
The conventional approach to density measurement, however, suffers from many drawbacks and disadvantages. First, when additional channels are utilized, the VoIP device may consume more MIPS per channel than the number of MIPS for a single channel. This is because more overhead is added due to the interaction between the active channels. Second, the voice quality may degrade as more channels are utilized. Third, the test signals may not provide a real-world complexity for an accurate density measurement. For example, the test signals may not cause echo cancellers to be engaged, or the test signals may create double talk conditions, which disturb the speech quality measurement.
Accordingly, there is a need in the art for method and system of measuring density of VoIP devices, which provide a more accurate representation of the density based on real-world conditions.